I get it now, the girl actually was in coma (symbolised as snowing) because of the brain dead, symbolised as half of her head missing in the dream, (caused by injury in her head or germs-like things because of the creature that she found on her journey i don't know, probably the second reason because the creature wants to kill the girl caused by the germs was getting uncontrollable) all things that she experienced and we saw was just a dream while she was in comatose, when the doctor finally injects the cure to her, (thats why the tower looks like a syringe, and the name of the cure on the bottle start with tet-, probably tetteleposan, thats why the girl can only say the word Tetteleposan and searching for it, because she probably still hearing doctors says it while she was in coma), when the cure works, the creature slowly fading because the cure kill it and snow stopping means that she is awake again